The invention is based on a method as generically defined by the preamble to the independent claims.
One such method is known for instance from German Patent Disclosure DE 199 03 936 A1. In this method, a motor vehicle is operated at least intermittently by an internal combustion engine and at least intermittently by at least one of two electrical machines. The motor vehicle has a transmission, with an input shaft, an output shaft, and two independently controllable power paths. Each power path is coupled to one of the two electrical machines and to the input shaft via a respective epicyclic gear and can be coupled to the output shaft via shiftable gears. If one gear is selected in each power path, then power can be transmitted to the output shaft simultaneously over both power paths.
This method has the advantage that with a transmission of relatively simple mechanical construction, good efficiency can be achieved. However, the possibility exists that a circulating mechanical power flow can arise in the power paths. Moreover, upon startup or starting of the internal combustion engine, one additional gear must first be selected, which at that instant in the affected power path causes an interruption in the tractive force. Then the engine brake must also be released. Both situations involve losses, which reduce the efficiency.